Targeted Therapies for Follicular Lymphoma.

Follicular lymphoma (FL) is the 2nd most common lymphoma in the USA/Western Europe. While incurable, the majority of patients are able to survive at least a decade with this disease. Response duration though varies, and subset of patients will relapse within 24 months of initial therapy (POD24). These patients have shortened survival compared to those who achieve more durable responses. Treatment interventions for patients are varied and include observation, radiation, or systemic therapies. Treatment outcomes have improved considerably over the last several decades with the introduction of new agents such as the CD 20 antibody rituximab and more recently with the advent of more targeted therapy. Most of the newer agents work differently from cytotoxic chemotherapy and either inhibit tumor-specific mutations, survival pathways, or harness the immune systems. While outcomes with traditional cytotoxic agents have been historically poor in certain subtypes such as POD24 and rituximab refractory disease, the reported outcomes with the newer agents have been encouraging as evident by several new drug approvals in FL. The biggest impact has been in the relapsed/refractory setting where we have approval of the immunomodulatory agent lenalidomide given in combination with rituximab. Based on the AUGMENT study, this agent has been approved for patients with R/R FL after one previous line of therapy. The EZH2 inhibitor, tazemetostat, was approved recently for patients with a known EZH2 mutation after one prior line of therapy or for FL patients who are deemed intolerant to other agents given the impressive safety profile in all patients. Finally, there is a plethora of agents that are designed to harness the immune system to combat this lymphoma. The data for these agents is still very early but nonetheless very impressive. In summary, FL is an incurable lymphoma without any standard of care options but has numerous treatments that have demonstrated some degree of efficacy. Recently we have made enormous strides in the understanding of some of the biological drivers of this disease which has allowed for refinement of treatment options. Moving forward, I would anticipate that we will continue to explore the use of agents that target specific mutations or utilize the immune system to hopefully one day achieve a cure.

Accurate dosimetry in 131I radionuclide therapy using patient-specific, 3-dimensional methods for SPECT reconstruction and absorbed dose calculation.

UNLABELLED: (131)I radionuclide therapy studies have not shown a strong relationship between tumor absorbed dose and response, possibly due to inaccuracies in activity quantification and dose estimation. The goal of this work was to establish the accuracy of (131)I activity quantification and absorbed dose estimation when patient-specific, 3-dimensional (3D) methods are used for SPECT reconstruction and for absorbed dose calculation. METHODS: Clinically realistic voxel-phantom simulations were used in the evaluation of activity quantification and dosimetry. SPECT reconstruction was performed using an ordered-subsets expectation maximization (OSEM) algorithm with compensation for scatter, attenuation, and 3D detector response. Based on the SPECT image and a patient-specific density map derived from CT, 3D dosimetry was performed using a newly implemented Monte Carlo code. Dosimetry was evaluated by comparing mean absorbed dose estimates calculated directly from the defined phantom activity map with those calculated from the SPECT image of the phantom. Finally, the 3D methods were applied to a radioimmunotherapy patient, and the mean tumor absorbed dose from the new calculation was compared with that from conventional dosimetry obtained from conjugate-view imaging. RESULTS: Overall, the accuracy of the SPECT-based absorbed dose estimates in the phantom was >12% for targets down to 16 mL and up to 35% for the smallest 7-mL tumor. To improve accuracy in the smallest tumor, more OSEM iterations may be needed. The relative SD from multiple realizations was <3% for all targets except for the smallest tumor. For the patient, the mean tumor absorbed dose estimate from the new Monte Carlo calculation was 7% higher than that from conventional dosimetry. CONCLUSION: For target sizes down to 16 mL, highly accurate and precise dosimetry can be obtained with 3D methods for SPECT reconstruction and absorbed dose estimation. In the future, these methods can be applied to patients to potentially establish correlations between tumor regression and the absorbed dose statistics from 3D dosimetry.